ACCEPTOR STEM AND ANTICODON RNA HAIRPIN HELIX INTERACTIONS WITH GLUTAMINE TRANSFER-RNA SYNTHETASE

The class I glutamine (G1n) tRNA synthetase interacts with the anticodon and acceptor stem of glutamine tRNA. RNA hairpin helices were designed to probe acceptor stem and anticodon stem-loop contacts. A seven-base pair RNA microhelix derived from the acceptor stem of tRNA(G1n) was aminoacylated by G1n tRNA synthetase. Variants of the glutamine acceptor stem microhelix implicated the discriminator base as a major identity element for glutaminylation of the RNA helix. A second RNA microhelix representing the anticodon stem-loop competitively inhibited tRNA(G1n) charging. However, the anticodon stem loop microhelix did not enhance aminoacylation of the acceptor stem microhelix. Thus, transduction of the anticodon identity signal may require covalent continuity of the tRNA chain to trigger efficient aminoacylation.